I am not a lawyer, but...

I was complaining about this to a friend of mine, and his response?

"If they rescale the image on the server, wouldn't they be creating a derivitive work?  As the copyright holder, you have to give permission for them to do that."

Sure, it would just be a TOS update to manage that, but I don't know how they could retroactively apply that to all the previously posted images.

Or, maybe... maybe we could just go back to having the full-sized image, eh?